ES2315292T3 - PROCEDURE AND EQUIPMENT FOR THE DIRECT PRODUCTION OF FINE METAL STRIP WITHOUT CASCARILLA. - Google Patents

Abstract

A method for the direct production, from molten metal, of scale-free thin metal strip. Hot thin metal strip exiting a continuous caster system is directed to a reducing chamber wherein a reducing gas reduces strip surface oxides while the cast metal strip is at an elevated temperature from retained heat from the molten metal. A cooling unit following the reducing chamber is used to cool the strip to a temperature below about 150° C. prior to exposing the strip to an oxidizing atmosphere. In various embodiments of the invention, strip thickness is reduced with use of hot and cold rolling mills and the scale-free surface of the strip is coated with protective coatings.

Description

Procedure and equipment for production Direct thin metal strip without scale.

Field of the Invention

The present invention is a process for Direct production from molten metal of a strip of metal without caliber shell finished by continuous casting of A hot thin strip. Rust removal from the surface It is with a reducing gas while the thin and hot metal strip of laundry is at a high temperature because of the heat retained from the molten metal.

Background of the invention

The production of a rolled steel strip flat, by the procedures of the current state of the art, is performed by continuous casting of refined steel to get a thin plate, followed by hot rolling of the plate to reach a thickness that can be put in the form of a coil for further processing. In that procedure, the surface hot rolled steel is very oxidized in the processing steps carried out at an elevated temperature while exposed to the atmosphere. Such oxides (husk) typically they consist of Fe 2 O 3, Fe 3 O 4 and FeO. A Next stage in the production of a rolled steel strip Flat typically involves removing oxides by processing the strip in a pickling acid solution before rolling the strip to the gauge finished in a cold rolling mill.

Current processing procedures of a Flat rolled steel strip require the use of equipment hot and cold rolling requiring significant expenses of capital, large amounts of energy to operate and a large Installation of machinery for installation. In addition, the use of acid stripping solutions to remove oxides from the surface and the elimination of spent acid solution present  environmental problems that are having as a consequence tighter regulations and increased costs for the elimination.

In an effort to reduce or eliminate hot or cold rolling stages, are being developed procedures for continuously casting a thin strip that Approximate the thickness of the finished gauge. However, there are still oxides present on the surface and problems continue to exist associated with rust removal with the use of solutions pickling acids. WO / 12233 discloses a procedure and equipment for reducing the scale of the surface of the strip. It includes the phases of heating the strip, reducing the rust husk and cool the strip.

Object of the invention

The object of the present invention is provide a procedure to produce a thin strip of steel with surface finish free of oxides, without the use of acid pickling solutions and without the use of equipment gives Extensive hot and cold rolling.

Summary of the Invention

The present invention is a process for Direct production of a thin strip of metal without scale to from molten metal by continuous casting of the metal to get a thin and hot metal strip and while the strip of casting still retains heat from molten metal, make it pass to through a chamber that contains a reducing gas to eliminate oxides of the surface of the strip so that a strip is produced Metal without oxides on the surface. The hot strip cools then to a temperature below about 150 ° C before exposing the surface of the strip to any atmosphere oxidizing In other embodiments of the invention, lamination in hot thin and hot metal strip and / or lamination in cold of the thin strip of cooled metal are carried out to reduce the thickness of the strip and modify the mechanical properties of the metal. In other embodiments of the invention, the surface of the thin strip of cooled metal is brushed, it re-textures or is coated with a coating protective or decorative

Other specific characteristics of the invention are described in more detail with reference to attached drawings.

Brief description of the drawings

fig. 1 is a schematic illustration of a embodiment of the process of the invention to produce a thin strip without scale incorporating a lamination stage in heat before cleaning the strip;

fig. 2 is a schematic illustration of a embodiment of the process of the invention to produce a thin strip without scale incorporating a rolling operation cold after a cooling stage of the strip;

fig. 3 is a schematic illustration of a embodiment of the process of the invention to produce a thin strip without scale incorporating means for cutting the strip in discrete pieces;

fig. 4 is a schematic illustration of a embodiment of the process of the invention to produce a thin strip without scale incorporating a stage of re-textured surface.

Detailed description of the invention

In Figures 1-4, the number 10 generally indicates a continuous thin strip fusion system to produce a thin and hot metal strip that has a thickness between approximately 0.5 and 4 mm. The molten metal 12, a product of an electric arc furnace, a furnace procedure Basic oxygen (BOF) or other source of molten metal is cast from continuous form until you get 14 thin and hot metal strip that exits the final casting rollers 16 of the fusion system keep going. The molten metal, continuously cast to achieve Thin and hot metal strip is steel.

The thin and hot steel strip 14 coming out of the continuous melting system 10 retains heat from molten metal 12 and the continuous fusion system is preferably controlled to download a thin and hot metal strip that has a surface temperature above about 400 ° C. The surface of the thin and hot metal strip, which is normally exposes to a liquid cooling medium and the atmosphere while it sneaks, it oxidizes strongly with a surface oxide that Contains Fe 2 O 3, Fe 3 O 4, FeO or combinations of those oxides, depending on the conditions during the operation of wash.

The thin and hot metal strip 14 (figure 1) which has a surface temperature above about 400 ° C, enters the reducing chamber 18, which encloses an atmosphere of reducing gas. An example of a reduction chamber 18 is the type described in the pending US patent application for processing with serial number 09 / 144.003 filed on August 31 1998 on behalf of Stephen L. Feldbauer and in the application for US patent pending processing with serial number 09 / 614,979 filed on June 1, 2000 on behalf of Stephen L. Feldbauer and Brian Braho, both assigned to the assignee of the present invention and both are incorporated herein as reference. The reducing chamber 18 contains such a reducing gas like hydrogen or carbon monoxide, hydrogen being the gas preferable. The thin and hot metal strip 14 moves through of chamber 10 in a direction indicated by arrow 20, while that the movement of the reducing gas is generally in one direction opposite, as indicated by arrows 22. The gas leaves the chamber 18 by means of a vent 24 that can include a combustion medium, such as a flame, for the combustion of reducing gases not consumed leaving the camera, so that safe operation is provided. The reduction of the surface oxides of the strip in the chamber reducer is optimized by providing a vigorous gas application reducer to the surface of the strip. In a preferred embodiment the reducing gas is continuously introduced into the chamber through of openings in the gas manifolds and heads towards the surface of the strip at a speed that creates turbulence with the impact with the strip. The reducing action of the gas on the oxide of the surface acts to reduce oxides as well as to weaken and drop the oxide particles on the surface of the strip, not being necessary, therefore, that each particle of the oxides or Oxide molecule react completely with the reducing gas. The loose oxides can be easily removed downstream by means mechanics such as brushing, described later. For ensure good contact of the reducing gas with strip 14, it can place fans (not shown) inside the chamber reducer to provide turbulence to the gas so that it Optimize the reduction reaction.

For proper operation of the reduction procedure, the surface temperature of the 14 thin and hot metal strip is above approximately 400 ° C The reduction reaction must take place over a period of very short time, since the strip may be moving through of the camera at a speed of up to 750 feet per minute (228.6 meters per minute). The thin and hot metal strip is at the temperature preferred only by the heat retained in the strip of the continuous casting operation of molten metal. He Strip cooling is controlled during casting in the system 10 continuous melting to provide enough heat for the Rust removal in the reducing chamber 18.

Means can be provided within the reduction chamber 18 for heating the thin and hot metal strip If the strip is not at the preferable temperature. In figure 1 it show radiant heaters 26, as an example, for Provide heat to the strip. The heaters 26 can be used during the start periods or the detention periods of the continuous fusion, which may be caused by problems of melting operation, so that they maintain the proper temperature for the surface of the strip. The heaters 26 are also necessary if a means of accumulation of strip is provided between the strip fusion system 10 and the reducing chamber 18. TO a strip accumulation medium is described below. In certain plants the use of heaters 26 may be necessary continuously if an optimal continuous fusion operation does not allow a thin and hot strip of casting metal to come out preferable temperature.

Online, immediately following the reduction chamber 18, is the cooling unit 28, in which the thin and hot metal strip 14 is cooled to a temperature below about 150 ° C in an inert atmosphere or reductive A reducing atmosphere is preferable since it may have place an additional reduction of surface oxides during an initial part of the cooling procedure while the Thin metal strip is still at an elevated temperature. Unit 28 cooling preferably connects directly to the reduction chamber 18 so that the thin metal strip 14 is not subjected to the atmosphere while at a temperature high.

The cooling is carried out in unit 28 cooling by introducing the cooling gas through collectors 30 and directing it towards the surface of the strip. The gas cooling is preferably an inert gas such as nitrogen combined with a reducing gas such as hydrogen. The closure 32 in the outlet end of cooling unit 28 and closure 34 in the inlet end of the reduction chamber 18 prevents the oxidizing gases from the atmosphere enter the system. A pressure positive inside the reduction chamber and the cooling unit It helps prevent the entry of oxidizing gases.

As described above, the particles non-adherent oxides may be present on the surface of the strip after the reduction reaction. The elimination of those particles are achieved with the use of a brushing unit 36 that provides brushes that act on the upper surfaces and bottom of the thin strip of cooled metal. Others can be used suitable means for particle removal.

The thin strip of metal cooled without scale leaving the brushing unit 36 is susceptible to oxidation and, if it is not scheduled for immediate additional processing, you can have an oil coating applied at station 38 of coating before it is rolled into a 40-strip tape drive. Alternative procedures may consist of applying others coatings in the coating station 38, such as a protective organic coating applied with a unit of organic coating or other more durable coatings, such as a hot dip galvanized applied with a hot dip galvanizing unit or coatings by electrolytic coating applied with a unit of electrolytic coating

In the production system the minus one hot rolling mill 42 between the fusion system 10 continuous and the reduction chamber 18. The system provides a procedure to properly reduce the finished caliber of the strip from the thickness of the strip leaving the fusion system keep going. The use of the hot rolling mill, which has as result a decrease in the temperature of the strip, can require additional use of heaters 26 in chamber 18 reducer to provide the oxide reduction temperature desired or, alternatively, the system 10 of continuous fusion of the strip so that the strip comes out at a temperature greater than preferable for the strip in the reduction chamber 18.

Figure 2 shows a procedure in which is provided at least one cold rolling mill 44 between the brushing unit 36 and coating station 38. Is it is preferable to place cold rolling mill 44 after unit 36 brushing so as not to embed any loose oxide particles in the Metal strip surface during cold rolling.

The inclusion of a cold rolling mill 44 in the Processing line allows the production of a thin metal strip which has a finished caliber smaller than that of the strip that leaves the 10 continuous fusion system. The use of a cold rolling mill 44 you can also provide a means to modify the properties strip mechanics. The use of a cold rolling mill 44 in combination with the hot rolling mill, in a single line of processed, can allow the production of a thin metal strip no scale of various thicknesses that has a range of mechanical properties. Thicknesses that vary from approximately 0.3 to 3.5 mm are possible using only the lamination stage in Hot or cold rolling or hot rolling stage and cold rolling combined.

Figure 3 represents a processing line in which produces discrete pieces of 46 fine metal without husk The processing line to produce discrete parts includes backing rollers 48, or other means, to maintain the strip tension, followed by cutting means, such as a shear 50, to cut the continuous strip into discrete pieces. The configuration of the processing line before shear 50 can be as described in any of the embodiments previous.

In figure 4 a station 52 of processed that has means to re-texturize the surface of a thin strip 14 of metal. The surface re-textured may include, for example, a pickling surface, obtained with the use of a pickling unit superficial, a "brushed" surface appearance, obtained, for example, with a thread brushing unit, a embossed surface, obtained with the use of an embossing unit, etc. Figure 4 shows a hot rolling mill and also Laminators are possible as shown in the configurations described above.

Although specific materials have been exposed, parameters and processing steps for the purpose of describing the embodiments, various modifications can be made, to the view of the previous teachings, without departing from the novel contributions from the applicant; therefore to determine The scope of the present invention should be referred to attached claims.

Claims (14)

1. A procedure for direct production of a thin strip of steel without scale from molten metal, which comprises the following stages:

to)

strain a thin and hot steel strip of a fusion system (10) continuous thin strip, in which the surface of the thin strip and hot steel is exposed to a cooling medium and to the atmosphere while straining,

b)

decrease the thickness of the thin strip and hot steel up to a predetermined caliber using a steel hot rolling,

C)

do pass the hot thin strip directly through a chamber (18) reducer at a first temperature above 400ºC, while that the thin and hot metal strip still retains heat from the metal melted so that it is at said first temperature only by the said heat retained.

d)

put on in contact the thin and hot steel strip in the chamber (18) reducer with a reducing gas to reduce oxides in the strip surfaces (14), and

and)

do pass the thin and hot steel strip (14), before exposure to an oxidizing atmosphere, directly from the reducing chamber to a cooling chamber (28), separated from said chamber (18) reducer, which has non-oxidizing cooling gas, directed towards the surfaces of the strip, so that the cooling of the thin and hot steel strip lowers its temperature below 150 ° C, to provide a thin strip of chilled steel.

2. Procedure for the direct production of a thin strip of metal without scale from molten metal according to claim 1, wherein the thin strip of chilled steel It is formed in a coil (40). 3. The procedure for direct production of a thin strip of steel without scale from molten metal according to claim 1, wherein, after cooling to a temperature below 150 ° C, the thin strip of cooled metal decreases its thickness to a predetermined caliber by cold rolling 4. The procedure for direct production of a thin strip of steel without scale from molten metal according to claim 1, wherein the thin and hot strip of metal has a thickness between 0.5 and 4 mm. 5. The procedure for direct production of a thin strip of steel without scale from molten metal according to claim 4, wherein, after the decrease of thickness, the thin strip of chilled steel has a thickness between 0.3 and 3.5 mm. 6. The procedure for direct production of a thin strip of steel without scale from molten metal according to claim 3, wherein, after the decrease of thickness, the thin strip of chilled steel has a thickness of 0.3 to 3.5 mm 7. The procedure for direct production of a thin strip of steel without scale from molten metal according to claim 1, wherein the thin steel strip is Brush after cooling. 8. The procedure for direct production of a thin strip of steel without scale from molten metal according to claim 7, wherein the brushed steel thin strip decreases its thickness to a predetermined caliber by cold rolling 9. The procedure for direct production of a thin strip of steel without scale from molten steel according to claim 7, wherein the brushed steel thin strip it has a coating applied to at least one of the surfaces. 10. The procedure for direct production of a thin strip of steel without scale from molten metal according to claim 9, wherein the coating is oil. 11. The procedure for direct production of a thin strip of steel without scale from molten steel according to claim 1, wherein the thin steel strip is cut in discrete pieces after cooling. 12. The procedure for direct production of a thin strip of steel without scale from molten steel according to claim 1, wherein the thin steel strip has a coating applied to at least one of the surfaces after the cooling. 13. The procedure for direct production of a thin strip of steel without scale from molten steel according to claim 12, wherein the coating is oil.

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14. The procedures for production direct of a thin strip of steel without scale from steel cast according to claim 1, wherein, after cooling, at least one of the surfaces of the thin strip of Chilled steel is re-textured.